The development of stategies and products to prevent the spread of antibiotic resistance is a national priority. A significant contributing factor in the rise of antibiotic resistance is the agricultural application of antibiotics which are used to treat human disease. We propose to develop an novel anti-microbial therapy for bovine mastitis that would break farmer's dependence on human antibiotics. This Nisin based product would have three characteristics. First, it would be a highly effective treatment for mastitis. Second, it would be inherently safe for human consumption and thus raise minimal food residue concerns. Third, it would replace antibiotics that are known to select for resistance to Class I and Il antibiotics used to treat human disease and therefore not contribute to the problem of antibiotic resistance. PROPOSED COMMERCIAL APPLICATION: The current annual US market for antibiotics intended to treat mastitis is 10 million doses. The market leader sells for $1.7 per dose. Thus, the projected market for this product is $17 million per year in the US alone.